BRAIN RESEARCH ELSEVIER Brain Research 640 (1994) 352-356 Short Communication Adrenalectomy increases the number of substance P and somatostatin immunoreactive nerve cells in the rat lumbar dorsal root ganglia R. Covefias a M. DeLe6n a, G. Chadi a A. Cintra a,* j._~ Gustafsson b J.A. Narvaez c, K. Fuxe a a Department of Neuroscience, Karolinska Institute, Box 60400, S-171 77, Stockholm, Sweden, b Department of Medical Nutrition, Huddinge Universitary Hospital, Huddinge, Sweden, c Department of Physiology, University of Mdlaga, Campus de Teatinos s / n , 29080, Mdlaga, Spain (Accepted 21 December 1993) Abstract Using an immunocytochemical technique we have analyzed changes in substance P, somatostatin, caicitonin gene-related peptide, and galanin immunoreactivity pattern in the rat dorsal root ganglia. After 7 days of adrenalectomy, sham operated rats were compared with adrenalectomized animals either receiving a daily intraperitoneal injection of 10 mg/kg b.wt. corticosterone or vehicle. Three lumbar ganglia from each animal were blocked, serially cut, and immunostained for each neuropeptide by means of the biotin-avidin-peroxidase technique. A systematic sampling of immunoreactive ganglion cells was performed and the sample number of immunoreactive ganglion cells was calculated. After adrenalectomy, the number of substance P and Somatostatin immunoreactive ganglion cells markedly increased ((means + S.E.M.): 245 ___ 68 versus 123 + 12 for sham operated animals, P < 0.01 (substance P) and 42 + 8 as compared to 22 + 9 for sham operated animals, P < 0.01 (somatostatin)). No significant changes were found in the number of calcitonin gene-related peptide and galanin immunoreactive cells after adrenalectomy. These results suggest that adrenal steroid hormones may reduce the synthesis of both substance P and somatostatin in the dorsal root ganglion cells. Daily treatment with a high dose of corticosterone, mimicking its serum levels after stress, failed to prevent the increase of peptide contents after adrenalectomy. These observations also indicate that a tonic action of corticosterone on mineralocorticoid receptors may be crucial for peptide regulation in the spinal ganglia. These results may be of relevance to adrenalectomy induced changes in sensory mechanisms, neurogenic inflammation and pain transmission and to a role of substance P and somatostatin in these processes. Key words: Glucocorticoid; Adrenalectomy; Immunocytochemistry; Calcitonin gene-related peptide; Substance P; Galanin; Somatostatin; Dorsal rool ganglia Within the dorsal root ganglia there exist distinct cell populations of substance P (SP), calcitonin gene- related peptide (CGRP), galanin (GAL) and somato- statin (SOM) immunoreactive (ir) primary sensory neu- rons [5,7,8,10,11,15,19,20]. These neurons may partici- pate in pain transmission and neurogenic inflamma- tion. In view of the potent analgesic actions of gluco- corticoids, it has been studied whether adrenalectomy and dexamethasone treatment substantially modulate neuropeptide contents of the dorsal root ganglion in the rat [18]. The SOM content in the cervical dorsal * Corresponding author. Department of Neuroscience, Division of Cellular and Molecular Neurochemistry, Karolinska Institute, Box 60400, S-171 77, Stockholm, Sweden. Fax: (46) (8) 337941. 0006-8993/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0006-8993(93)00010-A root ganglia was found to be reduced, while substance P and CGRP contents were found to be increased after adrenalectomy. Dexamethasone treatment was shown to reverse the actions induced by adrenalectomy [18]. Also the vagus sensory neurons have been found to be influenced by glucocorticoids in terms of SP contents [13] and in terms of axonal transport of substance P [12]. We have recently demonstrated the existence of glucocorticoid receptor (GR) immunoreactivity (IR) within SP and CGRP co-storing neurons of the lumbar spinal ganglia [2,3] emphasizing a possible direct influ- ence of glucocorticoids on the SP/CGRP containing primary sensory neurons. In the present study by means of immunocytochemi- cal technique and systematic sampling analysis, we have evaluated adrenalectomy induced changes in SP,